A multi-SIM (subscriber identity module) wireless device, including particularly mobile devices such as mobile phones (including so-called “smart phones”), personal digital assistants, tablet and laptop computers, etc., can hold two or more SIM cards. Currently, such devices can typically hold two SIM cards, though phones that can hold three SIM cards are now available and it is likely that phones and other wireless devices that can hold more SIM cards will become available.
Multi-SIM operation allows the use of multiple services without the need to carry several devices at the same time. For example, in the case of a dual-SIM device, the same handset can be used for business and private use with separate numbers and bills. As another example, the same handset can be used for travel, with one SIM being for use in the home country and the other SIM being for the country visited. As another example, both SIMs may be used with the same network operator, for example to achieve a higher total bandwidth for data connections. As yet another example, the device may contain both cellular and non-cellular radios which are used for voice and data communication respectively using the different SIMs. In any event, using multiple SIMs allows the user to take advantage of different pricing plans for calls and text messages to certain destinations as well as mobile data usage, and/or to keep personal and business use separate for example, and/or to achieve higher bandwidth, and/or to obtain coverage across different networks using a single handset. With this multiple SIM functionality, the SIMs can in general be from any network operator.
There are several types of multiple SIM devices known in the prior art. For example, a Dual SIM Dual Standby device can support two SIMs, which can simultaneously use one modem. Such devices are able to camp on two networks simultaneously, allowing the user to choose which SIM they want to use. However, these devices can only support an active voice call or data session to one SIM at a time, and the unused SIM is redundant during such sessions and remains in a standby mode.
As a further example, a Dual SIM Dual Call device can support two SIMs each connected to a different modem. Such devices can support voice calls and data sessions via both SIMs simultaneously, allowing, for example, one SIM to be engaged in a call session and the other SIM to be simultaneously engaged in a data session. There is growing demand for multi-SIM devices which can support a plurality of SIMs in call/data sessions simultaneously. However, this requires a plurality of modems to connect to the plurality of SIMs. Increasing the number of modems in a wireless device can substantially increase the cost of the device, particularly if the modems are sophisticated, “high end” modems.